This is the equation of a straight line. When the line crosses the x-axis that is the x- intercept, the corresponding y-coordinate will be zero. Substituting y = 0 into the equation and solving for x gives the x-intercept.
8x-(4×0)=-64
-8x=-64
x=8 <= the x-intercept.
Similarly, when the line crosses the y-axis the corresponding x- coordinate will be zero. Let x = 0 and solve for y.